I want to smooth only the outer faces of a circle
OK, for 3d Print this should work fine:


Add 2 edge loops along the sides.
Press CRTL num plus to extend your selection, so it covers the entire rim
W -&gt; subdivide
Choose these options (lower left at your VP imediately after hitting subdivide)


You might need to tweak the rim, bc. it may become concave. Easiest would probably to delete the new edge loops around the &quot;coin&quot; again.